Process for distilling benzyl chloride or mixtures containing benzyl chloride

ABSTRACT

The invention relates to an improved process for distilling benzyl chloride or mixtures containing benzyl chloride, which is carried out in the presence of a lactam, appropriately in an amount of between about 0.01 and about 1 percent by weight.

United States Patent Bockmann 1 5] Feb. 6, 1973 1541 PROCESS FORDISTILLING BENZYL [56] References Cited CHLORIDE 0R MIXTURES UNITEDSTATES PATENTS I CONTAINING BENZYL CHLORIDE 2,493,427 1/1950 Thomas..260/651 R [75] Inventor: Walter Bockmann, Krefeld-Uerdin- 2154212162/1951 y -260/651R gen Germany 2,542,225 2 1951 West .260/651 R-2,803,674 8/1957 Herberger et al.... ..260/651 R [73] Assignee: BayerAktiengesellschaft, Lev 3,535,391 10/1970 Kyker ..260/651 R kusen,Germany Primary Examiner-Wilbur L. Bascomb, Jr. [22] 'Flled: 1970Attorney-Connolly and Hutz [21] App1.N0.: 100,847

. [57] ABSTRACT 52 11.5. C1. ..203/6 203/58 260/651 invention relates toan improved ProSS for 51 1111.01. ..B01d 3/34 (3070 25/14 distillingbenzyl Chloride or i res ntaining benzyl [58] Field 01 Search ...203/6 758- 260/651 chloride which is carried presence of a tam, appropriate1yin an amount of between about 0.01 and about 1 percent by weight.

5 Claims, No Drawings PROCESS FOR DISTILLING BENZYL CHLORIDE OR MIXTURESCONTAINING BENZYL CHLORIDE The invention relates to an improved processfor distilling benzyl chloride or mixtures containing benzyl chloride.

It is known that benzyl chloride splits off hydrogen chloride relativelyeasily, especially at high temperatures, to form valueless, in mostcases deeply colored,

condensation products. Even traces of metals and of their compounds,especially iron oxides and iron salts, which can never be entirelyavoided in industry without great effort, greatly promote thisdecomposition.

The decomposition of benzyl chloride manifests itself particularlyunpleasantly when distilling benzyl chloride or mixtures containingbenzyl chloride, for example mixtures with benzal chloride andbenzotrichloride, such as arise in the industrial manufacture of benzylchloride, since the distillation columns clog already within arelatively short time, through deposition of the condensation products,and undistillable residues become enriched in the sump.

It has been found that the decomposition of benzyl chloride and thedisadvantages on distillation which are connected therewith are largelyavoided by adding a lactam.

Accordingly, the invention consists in the distillation, in the presenceof a lactam, of benzyl chloride or of a mixture containing benzylchloride.

The lactam is appropriately present inan amount of between about 0.01and about 1.0 per cent by weight,

referred to the weight of benzyl chloride or mixture containing benzylchloride to be distilled.

Suitable lactams are, for example, pyrrolidone-(Z), e-caprolactam,capryllactam and w-lauryllactam.

The stabilizing effect of the addition of lactams is shown by thefollowing test:

1 per cent by weight of sublimed iron-(III) chloride and 0.1, 0.5 and1.0 per cent by weight of various lactams were added to pure benzylchloride. The degree of decomposition of the benzyl chloride in weightper cent after 90 minutes, as measured from the amount of hydrogenchloride split off, was then determined at room temperature, at 50 C andat 95 C, as is shown by the Table below:

Degree of decomposition .determined detennined Pyrrolidone-(2) 0.l l0 9196 0.5 8 15 66 L0 l0 l2 l3 not not Caprolactam 0| )4 determineddetermined 0.5 13 35 8 1.0 13 21 16 capryllactam 0.l 87 95 notdetermined 0.5 8 70 75 1.0 8 l4 17 not Lauryllactam 0.l 72 94 determinednot 0.5 22 94 determined 1.0 l0 17 30 On distilling benzyl chloride froman industrial mixture of toluene, benzyl chloride, benzal chloride andbenzotrichloride, a decomposition which is only barely still measurableoccurs in the presence of merely about 0.01 to about 0.05 per cent byweight of caprolactam, since the starting material only contains tracesof metal compounds which cause decomposition, in contrast to the abovetests, which were carried out with a comparatively very high ironchloride content.

Since the boiling point of the lactams is very much higher than that ofthe toluene chlorination products, it is practically impossible todistil portions of lactam at the same time. This avoids the desireddecompositioninhibiting action during the distillation becoming anundesired reaction-inhibiting action during the further use of thebenzyl chloride.

What we claim is:

1. In theprocess of recovering benzyl chloride as overhead from amixture containing benzyl chloride and a metal compound impurity bydistillation, the improvement which comprises carrying out saiddistillation in the presence of from about 0.01 to about 1.0% by weight,based on the weight of the mixture of a lactam selected from the groupconsisting of pyrrolidone- (2), e-caprolactam, capryllactam andw-lauryllactam.

2. The improved process of claim 1 wherein said metal compound is ferricchloride.

3. The improved process of claim 1 wherein said mixture comprises benzylchloride, benzal chloride, benzotri-chloride and said metal compoundimpurity.

4. A mixture comprising benzyl chloride and from 0.1 to 1.00/0 by weightof a lactam selected from the group consisting of pyrrolidone-(Z),e-caprolactam,

capryllactam and m-lauryllactam.

' 5. A process for inhibiting the decomposition of benzyl chloride whichcomprises adding to said benzyl chloride 0.1 to 1.00/0 by weight of alactam selected from the group consisting of pyrrolidone-(Z),c-caprolactam, capryllactam and w-lauryllactam.

1. In the process of recovering benzyl chloride as overhead from amixture containing benzyl chloride and a metal compound impurity bydistillation, the improvement which comprises carrying out saiddistillation in the presence of from about 0.01 to about 1.0% by weight,based on the weight of the mixture of a lactam selected from the groupconsisting of pyrrolidone-(2), epsilon -caprolactam, capryllactam andomega -lauryllactam.
 2. The improved process of claim 1 wherein saidmetal compound is ferric chloride.
 3. The improved process of claim 1wherein said mixture comprises benzyl chloride, benzal chloride,benzotri-chloride and said metal compound impurity.
 4. A mixturecomprising benzyl chloride and from 0.1 to 1.0% by weight of a lactamselected from the group consisting of pyrrolidone-(2), epsilon-caprolactam, capryllactam and omega -lauryllactam.